JP2014518559A - Aluminum oxide paste and method of using the same - Google Patents

Abstract

The present invention relates to an aluminum oxide paste and a method of using the aluminum oxide paste for the formation of an Al ₂ O ₃ coating or a mixed Al ₂ O ₃ hybrid layer.

Description

The present invention relates to an aluminum oxide paste and a method of using the aluminum oxide paste for the formation of an Al ₂ O ₃ coating or a mixed Al ₂ O ₃ hybrid layer.

The synthesis of sol-gel based layers is gaining increasing importance in industrial production due to its versatile availability. Thus, the following functional layers or surface finishes and modifications can be constructed or implemented utilizing sol-gel technology:
・ Anti-reflective coatings for optical components, etc. ・ Corrosion-resistant coatings such as steel ・ Scratch-proof coatings ・ Surface seals ・ Hydrophobization or hydrophilization of surfaces ・ Synthesis of membranes and membrane materials ・ Support for catalytic applications Material synthesis and precursors of sintered ceramics and sintered ceramic parts

Dielectric layers for electronics and microelectronic components having the following specific applications, where formation of one of the desired functions is O ₂ , N ₂ , O ₂ / N ₂ and / or forming gas flow May be related to a specific heat treatment, such as, but not necessarily:
Spin-on-glass (“SoG”) in integrated circuit production
• Dielectric buffer layers ("porous MSQ") between individual metallization surfaces in the production of integrated circuits
-Printable dielectric layers for printed circuits, general printable electronics, especially printable organic electronics

・ Diffusion buffer layer (see MERCK SolarResist patent)
For general semiconductors, for silicon, in particular for silicon wafers, in particular for the production of crystalline silicon solar cells, dopants for specific overall and / or local doping of the following (for example B, Ga, P) , As, etc.) Matrix for bonding-General semiconductors-Silicon, especially for the manufacture of silicon wafers, especially crystalline silicon solar cells-General semiconductors that result in a considerable reduction in surface recombination rates Electronic passivation of surfaces, especially silicon surfaces.

This list only represents a selection of various application possibilities.
Most sol-gel methods known from the literature are specific hydrolysis and condensation that makes it very easy to synthesize silicon and its alkoxides (siloxanes), networks with different properties and coatings that can be derived from them. Thus, a smooth or porous film or a film with embedded particles can be produced in this way. However, for certain applications, it is desirable to provide coatings with improved properties, such as higher hardness and modified behavior for commonly used etchants compared to conventional silicon dioxide layers.

With numerous experiments, it has been found that the use of Al ₂ O ₃ in the corresponding layer makes it possible to obtain a very promising alternative to the SiO ₂ layer. Al ₂ O ₃ acts as either a doping source diffusion barrier and / or sol-gel-based, in addition to the use of the above-mentioned, thanks to the hardness of its crystalline modifications, Al ₂ O ₃ is used as a mechanical protection layer Also suitable for.

Surprisingly, it was possible to synthesize and form pasty mixtures based on the Al ₂ O ₃ sol-gel process, which has now been found to meet the rheological requirements of screen printing processes. Unexpectedly, the paste-like mixture can be applied to the silicon wafer surface surprisingly easily in a screen printing process, and they have a high structural fidelity.

  Especially for use in the solar sector, sol-gel based layers must meet certain requirements, and so are pastes based on them, ie these requirements are for the production of such layers. Also in the formation of the other compositions must be considered.

On the other hand, a suitable solvent should be selected that has advantageous properties for the use, such as non-toxic to low toxicity, moderate surface wetting, etc. Furthermore, corrosive anions (such as Cl ⁻ or NO ₃ ^— ) greatly limit the possibilities of using the paste, so they should not be present in the paste. Corresponding pastes, for example, corrode the printing and vapor deposition equipment used, and further promote corrosion of solder joints, which is undesirable later when connecting solar cells provided with such layers, and consequently As such, it can result in limitations on the long-term stability of crystalline silicon solar cells.

  With regard to the production of screen-printable pastes, the literature only discloses synthesis using rheological additives, or grinding of metal oxides precipitated by a sol-gel method, followed by suspension of these oxides. However, this type of paste production with post-treatment or mixing of rheological additives usually involves actual active substance contamination.

Zhou et al. Studied, for example, the synthesis of Cu ₂ ZnSnS ₄ paste. Ethanol was added and the elements copper, zinc, tin and sulfur were ground in a ball mill. After subsequent drying, they were suspended in isopropanol and mixed with a 10% ethylcellulose mixture in isopropanol. Terpineol was added and the mixture was ground again in a ball mill and the alcohol was removed in vacuo. The resulting viscous mass was used for screen printing and the resulting layer was studied. {[1] Z. Zhou, Y. Wang, D. Xu, Y. Zhang, Solar Energy Materials and Solar Cells, in press, (2010)}

Hansch et al. Next studied the synthesis of screen-printable Y ₂ O ₃ / ZrO ₂ mixed oxides. By mixing Y ₂ O ₃ / ZrO ₂ sol with acetylacetone and zirconium n-propoxide stabilized with isopropanol and carboxylic acid (acetic acid, propionic acid, caproic acid, nonanoic acid) in aqueous yttrium nitrate solution. Obtained. To obtain a screen printable paste, calcined Y ₂ O ₃ / ZrO ₂ powder is added to the sol (sol / powder 20 / 80-40 / 60 wt%) and the mixture is subsequently ground using a ball mill And homogenized. Similarly, pastes were prepared by adding organic additives (terpineol or ethyl cellulose), but pastes were also prepared only from calcined oxide. These pastes were studied for their suitability as electrolytic layers in fuel cells. {[2] R. Hansch, MRR Chowdhury, NH Menzler, Ceramics International, 35 (2009), 803-811}

Laobuthee et al. By mixing milled (K ⁺ or Na ⁺ doped) MgAl ₂ O ₄ powder formed from sol-gel synthesis with organic additives (butyl carbitol acetate, terpineol, ethyl cellulose). MgAl ₂ O ₄ (spinel) paste was obtained. This paste was applied to an aluminum oxide substrate using screen printing. The layers thus obtained were studied for their suitability as atmospheric moisture sensors. {[3] A. Laobuthee, N. Koonsaeng, B. Ksapabutr, M. Panapoy, C. Veranitisagul, International Journal of Materials & Structural Reliability, 3 (2005), 95-103}

Riviere et al. Obtained from optimizing classic SnO ₂ screen printing paste with inorganic thickener and organic “medium” (solvent) and sol-gel synthesis with mixing of active SnO ₂ (SnO ₂ powder) An attempt was made to prepare a “gel ink” consisting only of SnO ₂ gel. These two compositions were studied for their suitability as CO sensors. Inks without added organic and inorganic additives showed significantly higher sensor activity after heat treatment at 600 ° C. {[4] B. Riviere, J.-P. Viricelle, C. Pijolat, Sensors and Actuators B, 93 (2003), 531-537}

After the classic sol-gel process, there is no stable state between sol (low viscosity <100 mPas) and gel (high viscosity> 100 Pas) for the production of Al ₂ O ₃ layers. The literature refers to stabilized sols or high viscosity gels for the formation of aluminum oxide fibers.

  Dressler et al. Added ASB (Al tri-sec-butoxide) to an aqueous solution of aluminum nitrate. At high ASB concentrations, phase separation (2-butanol phase and aqueous phase) occurred. Therefore, polyvinyl pyrrolidone was added as a binder. The rheology and chemical structure of the resulting sol was investigated using NMR and the correlated particle size was measured. {[5] M. Dressler, M. Nofz, J. Pauli, C. Jaeger, Journal of Sol-Gel Science and Technology (2008) 47, 260-267}

In addition, Glaubitt et al. Modified ASB first with glycol ether followed by propionic acid. After adding 0.5 moles of water per mole of aluminum, the viscosity increased rapidly (> 2000 Pas), leaving a clear sol (/ gel). The gel showed long stability and long fibers could be drawn from it. Prior to each modification, the sol was investigated using ²⁷ Al-NMR and drying was examined using TGA. {[6] W. Glaubitt, D. Sporn, R. Jahn, Journal of Sol-Gel Science and Technology, 2 (1994), 525-528}

Shojaie-Bahaabad et al. Next investigated the formation of Y ₂ O ₃ / Al ₂ O ₃ (YAG) sols. Yttrium oxide was dissolved in aqueous HCl. AlCl ₃ and aluminum powder were slowly added to this solution. The solution was heated at 98 ° C. for 6 hours to dissolve the aluminum powder. The resulting sol was rheologically investigated for its gel behavior as a function of Al powder for AlCl ₃ content and Y ₂ O ₃ and H ₂ O / HCl content. Fibers were spun from gel (η> 2000 Pas) and these were examined using SEM and XRD. {[7] M. Shojaie-Bahaabad, E. Taheri-Nassaj, R. Naghizadeh, Ceramics International, 34 (2008), 1893-1902}

Task:
The object of the present invention is therefore to develop screen-printable aluminum oxide pastes while preventing interference of highly corrosive anions such as chlorides and nitrates and further rheological additives that can lead to the introduction of further impurities. And to stabilize, where the long-term stability of the paste should be kept at the same time.

The subject of the invention is achieved by the use of a printable, sterically stabilized paste for the formation of Al ₂ O ₃ coatings and also mixed Al ₂ O ₃ hybrid layers. The paste of the present invention comprises a precursor for the formation of Al ₂ O ₃ and one or more of boron, gallium, silicon, germanium, zinc, tin, phosphorus, titanium, zirconium, yttrium, nickel, cobalt, iron, It includes an oxide of an element selected from cerium, niobium, arsenic, and lead, where the paste is obtained by introducing the corresponding precursor into the paste. Preference is given to the use of sterically stabilized pastes obtained by mixing at least one hydrophobic component and at least one hydrophilic component, optionally with at least one chelating agent.

  Furthermore, these pastes comprise at least one hydrophobic component selected from the group of 1,3-cyclohexadione, salicylic acid and structurally related compounds, and acetylacetone, dihydroxybenzoic acid and trihydroxybenzoic acid or Chelating agents such as structurally related compounds, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DETPA), nitrilotriacetic acid (NTA), ethylenediaminetetramethylenephosphonic acid (EDTPA) and diethylenetriaminepentamethylenephosphonic acid (DETPPA) Or at least one hydrophilic compound selected from the group of structurally related complexing agents or corresponding chelating agents.

  In addition to these components, the paste used is preferably a solvent selected from the group of low-boiling alcohols, preferably selected from the group of ethanol and isopropanol, and preferably diethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol At least one high boiling solvent selected from the group of high boiling glycol ethers, selected from the group of monobutyl ether or mixtures thereof, and optionally selected from the group of acetone, DMSO, sulfolane and ethyl acetate Polar solvents or similar polar solvents. Particularly advantageous is according to the invention of the corresponding paste having an acidic pH in the range of 4 to 5 and containing as acid an acid or acids, preferably acetic acid, thereby resulting in residue-free drying. Use.

Particular preference is given to the use of these pastes for the formation of an impermeable homogeneous layer, wherein water for hydrolysis is used in the range of 1: 1 to 1: 9, preferably 1 Is added in a molar ratio of water to precursor between 1.5 and 1: 1.25, where the solids range from 9 to 10% by weight. In particular, these pastes should be used for the manufacture of diffusion barriers, printed dielectrics, electrical and electronic passivators, anti-reflective coatings, mechanical protective layers against wear or chemical protective layers against the effects of oxidation or acid. Can do. These pastes further provide simple, polymeric boron and phosphorylation for the entire or local doping of semiconductors, preferably silicon, or for the production of Al ₂ O ₃ layers as sodium and potassium diffusion barriers in LCD technology. It is also suitable for the preparation of a hybrid material containing the product and its alkoxide.

In particular, the invention applies to single crystal or polycrystalline silicon wafers, sapphire wafers, thin film solar modules, glass coated with functional materials (eg ITO, FTO, AZO, IZO or the like), uncoated glass, steel It also relates to a method for producing a pure, residue-free, amorphous Al ₂ O ₃ layer on elements and alloys and on other materials used in microelectronics, where the application of the paste Thereafter, drying is carried out at a temperature between 300 and 1000 ° C., preferably at 300 to 400 ° C., particularly preferably at 350 ° C.
Drying and heat treatment of the printed paste at temperatures from 1000 ° C. forms a hard, crystalline layer with properties comparable to corundum.

By applying a suitable amount of paste per unit area, a layer with a thickness of less than 100 nm is obtained during a drying time of less than 5 minutes. The method of the present invention is preferably a pure, residue-free, amorphous, structurable Al ₂ O ₃ layer when drying is carried out at a temperature between 300-500 ° C. after application of a thin layer of paste. Can be manufactured. Drying at a temperature of <500 ° C., the layer obtained accordingly is etched with most mineral acids, but preferably with HF and H ₃ PO ₄ and with many organic acids such as acetic acid or propionic acid. Can be post-structured.

Surprisingly, experiments have shown that, based on the Al ₂ O ₃ sol-gel method, it is possible to synthesize and formulate a paste-like mixture that meets the rheological requirements of the screen printing method, and as described above. It has been shown that it can be found just in the viscosity window, which has not been acquired / occupied before. Unexpectedly, the pasty mixture, for example on a silicon wafer surface, is surprisingly easy on the one hand, and on the other hand it retains a very good high structural fidelity and is deposited using a screen printing method. Corresponding to the definitions or features used for screen printing, as shown in the examples below. The corresponding aluminum oxide paste forms a smooth layer which is impervious, ie diffusion-impermeable or resistant, on the surface of the silicon wafer. This means that in a combination of drying and heat treatment at less than 400 ° C., the paste formed by the gel-gel method forms a stable and smooth layer free from organic impurities after drying and heat treatment.

The present invention therefore, pH in the range of 4-5, preferably a pH <4.5, the acidic, a sterically stabilized _Al 2 _{O 3} paste, sterically stabilized _Al 2 O ₃ precursor, excellent wettability and SiO 2 _- and silane - having adhesive properties on the termination silicon wafer surface, including a small amount of polyoxyl solvents, homogeneous, impervious, especially diffuse non The paste relates to the formation of a permeable layer.
Figures and diagrams

Micrographs of screen printed Al ₂ O ₃ layout after drying for 5 minutes at 300 ° C. (left) and 10 minutes at 600 ° C. (right). Photomicrograph of Al ₂ O ₃ layout applied by screen printing after about 1000 preprints. Change in viscosity of screen printable aluminum oxide paste according to Examples 1 and 2. Charge-carrier lifetime of p-doped FZ wafer sample according to Example 5.

FIG. 1 shows a photomicrograph of an Al ₂ O ₃ layer applied to a polished (100) silicon wafer by screen printing and having a layer thickness of 600 nm at the crown. It will be clear to the person skilled in the art that the layer thickness that can be achieved is variable through appropriate and careful selection and setting of the characteristic parameters of the paste used and through the selection of the screen used for the printing method. is there.

Accordingly, FIG. 1 in this case shows micrographs of the screen-printed Al ₂ O ₃ layout after drying for 5 minutes at 300 ° C. (left) and after 10 minutes at 600 ° C. (right). Very good resolution of the line (printing: 500 μm, after drying: 500 μm) is clear. Debris in the screen printed layer probably occurs during the rupture of a layer having a thickness of about 600 nm.

Aluminum sols can be formulated using the corresponding alkoxide of aluminum as a precursor. These are aluminum triethoxide, aluminum triisopropoxide and aluminum tri-sec-butoxide. Alternatively, readily soluble aluminum hydroxides and oxides can be used. All organoaluminum compounds suitable for the formation of Al ₂ O _{3 in} the presence of water at acidic conditions with a pH in the range of about 4-5 are suitable per se as precursors in paste formulations.

  The corresponding alkoxide is preferably dissolved in a suitable solvent mixture. The solvent mixture can be composed of both polar protic and polar aprotic solvents, and mixtures thereof. Furthermore, according to pre-defined application conditions, solvent mixtures can be accommodated within wide limits by the addition of non-polar solvents, for example to influence their wetting behavior.

Preferred polar protic solvents can be:
Aliphatic, saturated and unsaturated, monobasic to polybasic, functionalized and non-functionalized alcohols,
-Methanol, ethanol, propanol, butanol, amyl alcohol, propargyl alcohol and homologues with C ≦ 10, etc.
Alkylated, secondary and quaternary alcohols having any desired degree of branching, such as isopropanol, 2-butanol, isobutanol, tert-butanol and congeners, preferably isopropanol and 2-butanol glycol, pinacol 1,2-propanediol, 1,3-propanediol, 1,2,3-propanetriol and further branched homologues, etc.
・ Monoethanolamine, diethanolamine, triethanolamine, etc.

Glycol ethers and condensed glycol ethers, and propylene glycol ethers, and condensed propylene glycol ethers, and branched homologues thereof,
・ Methoxyethanol, ethoxyethanol, propoxyethanol, butoxyethanol, pentoxyethanol, phenoxyethanol, etc.
・ Diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, diethylene glycol dipentyl ether, etc.
-Propylene glycol, methoxy-2-propanol, propylene glycol monomethyl ether, propylene glycol dimethyl ether, propylene glycol monoethyl ether, propylene glycol diethyl ether, phenoxypropylene glycol, and the like.

Preferred polar aprotic solvents can be:
Dimethyl sulfoxide, sulfolane, 1,4-dioxane, 1,3-dioxane, acetone, acetylacetone, dimethylformamide, dimethylacetamide, ethyl methyl ketone, diethyl ketone, and the like.

  In the case of the use of aluminum alkoxide, the synthesis of the sol requires the addition of further water to achieve hydrolysis for the formation of the aluminum nucleus and its precondensation. The required water can be added in deficient to excess equivalents. Substantial equivalent addition is preferred.

  By addition of organic acids and / or mixtures of organic acids, the alkoxide liberated by hydrolysis of the aluminum core is converted into the corresponding alcohol. The acid or acid mixture is added so that the pH is in the range between 4 and 5, preferably <4.5. In addition, the added acid and / or acid mixture serves as a catalyst for precondensation and for crosslinking initiated with aluminum nuclei that hydrolyze in solution.

Preferred organic acids can be:
Formic acid, acetic acid, acetoacetic acid, trifluoroacetic acid, monochloro-trichloroacetic acid, phenoxyacetic acid, glycolic acid, pyruvic acid, glyoxylic acid, oxalic acid, propionic acid, chloropropionic acid, lactic acid, β-hydroxypropionic acid, glyceric acid, Valeric acid, trimethylacetic acid, acrylic acid, methacrylic acid, vinylacetic acid, crotonic acid, isocrotonic acid, glycine and also α-amino acid, β-alanine, malonic acid, succinic acid, maleic and fumaric acid, malic acid, tartronic acid, Alkylated and halogenated, nitrated and hydroxylated benzoic acids such as mesoxalic acid, acetylenedicarboxylic acid, tartaric acid, citric acid, oxaloacetic acid, benzoic acid, salicylic acid, and further homologs.

  Stabilization of the aluminum sol can be accomplished by using the above organic acids and mixtures thereof, or alternatively can be achieved or increased by specific additions of complexing and / or chelating agents. Complexing agents for aluminum that can be used are the following substances:

Nitrilotriacetic acid, nitrilotris (methylenephosphonic acid). Ethylenediaminetetraacetic acid, ethylenediaminetetrakis (methylenephosphonic acid), diethyleneglycoldiaminetetraacetic acid, diethylenetriaminepentaacetic acid, diethyleneglycoltriaminetetrakis (methylenephosphonic acid),

Diethylenetetraminepentakis (methylenephosphonic acid), triethylenetetraminehexaacetic acid, triethylenetetraminehexakis (methylenephosphonic acid), cyclohexanediaminetetraacetic acid, cyclohexanediaminetetrakis (methylenephosphonic acid), etidronic acid, iminodiacetic acid, iminobis ( Methylenephosphonic acid), hexamethylenediaminetetrakis (methylenephosphonic acid), methyliminodiacetic acid, methyliminobis (methylenephosphonic acid), dimethyliminoacetic acid, dimethyliminomethylenephosphonic acid, hydroxyethyliminodiacetic acid, hydroxyethylethylenediaminetetraacetic acid, Trimethylene dinitrilotetraacetic acid, 2-hydroxytrimethylene dinitrilotetraacetic acid, maltol, ethyl maltol, isomaltol, kojic acid, mimosine Mimosine acid, Mimo Shin methyl ether,

1,2-dimethyl-3-hydroxy-4-pyridinone, 1,2-diethyl-3-hydroxy-4-pyridinone, 1-methyl-3-hydroxy-4-pyridinone, 1-ethyl-2-methyl-3- Hydroxy-4-pyridinone, 1-methyl-2-ethyl-3-hydroxy-4-pyridinone, 1-propyl-3-hydroxy-4-pyridinone, 3hydroxy-2-pyridinones, 3-hydroxy-1-pyridinethione , 3-hydroxy-2-pyridinethiones, lactic acid, maleic acid, D-gluconic acid, tartaric acid, 8-hydroxyquinoline, catechol, 1,8-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, naphthalic acid (naphthalene- 1,8-dicarboxylic acid), 3,4-dihydroxynaphthalene, 2-hydroxy-1-naphthoic acid, 2 Hydroxy-3-naphthoic acid, dopamine, L- dopa, Desferal or death ferri desferrioxamine -B, acetone hydroxamic acid,

1-propyl- and 1-butyl- and 1-hexyl-2-methyl-3-hydroxy-4-pyridinone, 1-phenyl- and 1-p-tolyl- and 1-p-methoxyphenyl and 1-p-nitro Phenyl-2-methyl-3-hydroxy-4-pyrimidine, 2 (2′-hydroxyphenyl) -2-oxazoline, 2- (2′-hydroxyphenyl) -2-benzoxazole, 2, X-dihydroxybenzoic acid ( Where X = 3, 4, 5, 6),

Other alkylated, halogenated, nitrated 2, X-dihydroxybenzoic acids, salicylic acid and its alkylated and halogenated and nitrated derivatives such as 4-nitro- and 5-nitrosalicylic acid, 3,4-dihydroxybenzoic acid, Other alkylated, halogenated, nitrated 3,4-dihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, other alkylated, halogenated, nitrated 2,3,4-trihydroxybenzoic acid, 2,3-dihydroxyterephthalic acid, other alkylated, halogenated, nitrated 2,3-dihydroxyterephthalic acid, mono-, di- and trihydroxyphthalic acid, and other alkylated, halogenated, nitrated derivatives thereof 2 (3 ′, 4′-dihydroxyphenyl) -3,4-dihydro-2H-1-benzopyran-3 5,7-triol (component from tannin)

Malonic acid, oxydiacetic acid, oxaloacetic acid, tartronic acid, malic acid, succinic acid, hippuric acid, glycolic acid, citric acid, tartaric acid, acetoacetic acid, ethanolamines, glycine, alanine, β-alanine, alanine hydroxamic acid, α Aminohydroxamic acids, rhodotorlic acid, 1,1 ′, 1 ″ -nitrilo-2-propanol, N, N-bis (2-hydroxyethyl) glycine, bis (2-hydroxyethyl) iminotris (hydroxymethyl) methane, N- (tris (hydroxymethyl) methyl) glycine, ethylenediaminetetra-2-propanol, N, N-bis (2-hydroxyethyl) -2-aminoethanesulfonic acid, N- (tris (hydroxymethyl) methyl) -2 -Aminoethanesulfonic acid, pentaerythritol, N-butyl- 2,2'-iminodiethanol, monoethanolamine, diethanolamine, triethanolamine, acetylacetone, 1,3-cyclohexanedione.

-Furthermore, substitutions of complexing and chelating agents (eg alkylation, halogenation, nitration, sulfonation, carboxylation) homologues and derivatives and their salts, preferably ammonium salts and Al can be coordinated It is also possible to use complexing agents and chelating agents.

In addition, additional additives can be added to the aluminum sol for specific settings, which can be desirable properties, such as surface tension, viscosity, wetting behavior, drying behavior, and adhesion capability. Such additives can be the following:
・ Surfactants and surface active compounds to affect wetting and drying behavior ・ Antifoaming and degassing agents to influence drying behavior,

-Further high and low boiling polar protic and aprotic solvents to influence particle size distribution, degree of precondensation, condensation, wetting and drying behavior, and printing behavior,
Additional high and low boiling nonpolar solvents to affect particle size distribution, degree of precondensation, condensation, wetting and drying behavior, and printing behavior,
Polymers to affect rheological properties (structural viscosity, thixotropy, pour point, etc.)
Fine particle additives to influence the rheological properties,
-Fine particle additives (eg aluminum hydroxide and aluminum oxide, silicon dioxide) to influence the thickness and morphology of the dried film after drying,
Fine particle additives (eg aluminum hydroxide and aluminum oxide, silicon dioxide) to affect the scratch resistance of the dry film,

-Boron, gallium, silicon, germanium, zinc, tin, phosphorus, titanium, zirconium, yttrium, nickel, cobalt, iron, suitable for the corresponding hybrid sol and allowing all mixture shapes obtained therefrom Oxides, hydroxides, basic oxides, alkoxides and precondensed alkoxides of elements selected from the group of cerium, niobium, arsenic, lead, and further compounds and mixtures thereof. In particular, these are simple boron and phosphorus polymer oxides, hydroxides, alkoxides for the formulation of compounds having a doping action on semiconductors, in particular silicon layers.

  In this connection, it goes without saying that each print coating method imposes a requirement on itself that the paste is printed and / or that the paste is derived from the corresponding ink. Depending on the particular printing method, the individual parameters of the paste are set in relation to the surface tension, viscosity and total vapor pressure of the paste.

  Apart from their use, for example in the manufacture of parts in the metal industry for the production of scratch- and corrosion-resistant layers, printable pastes are preferably used in the electronics industry, and in particular here in microelectronics, solar cells and microelectronics. It can be used in the production of mechanical (MEMS) parts. In this context, photovoltaic parts mean in particular solar cells and modules. Thus, pastes according to the present invention produce thin film solar cells from thin film solar modules, manufacture of organic solar cells, manufacture of printed circuits and organic electronics, thin film transistors (TFTs), liquid crystals (LCDs), organic light emitting diodes (OLEDs). And can be used for the manufacture of display elements based on touch sensitive capacitive and resistive sensor technology.

The present invention therefore also resides in the provision of a printable, sterically stabilized paste for the formation of Al ₂ O ₃ coatings and also mixed Al ₂ O ₃ hybrid layers.
Suitable hybrid materials include Al ₂ O ₃ and the elements boron, gallium, silicon, germanium, zinc, tin, phosphorus, titanium, zirconium, yttrium, nickel, cobalt, iron, cerium, niobium, arsenic, and lead. It is a mixture with oxides, where the paste is obtained by introducing the corresponding precursor into the paste. The steric stabilization of the paste can occur in hydrophobic components such as 1,3-cyclohexadione, salicylic acid and structural related substances, and in acetylacetone, dihydroxybenzoic acid, trihydroxybenzoic acid and their structural related substances. To the extent hydrophilic components, or ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DETPA), nitrilotriacetic acid (NTA), ethylenediaminetetramethylenephosphonic acid (EDTPA), diethylenetriaminepentamethylenephosphonic acid (DETPPA) and structure Resulting from mixing with a chelating agent such as a complexing agent or chelating agent.

Solvents that can be used in the paste are at least one low-boiling alcohol, preferably ethanol or isopropanol, and at least one high-boiling glycol ether, preferably diethylene glycol monoethyl ether, ethylene glycol monobutyl ether or diethylene glycol monobutyl ether, or A suitable mixture of pure glycol ethers. However, other polar media such as acetone, DMSO, sulfolane or ethyl acetate can also be used. The coating properties can be adapted to the substrate by its mixing ratio.
The addition of the acid achieves the acidic pH of the paste. The paste for precondensation is therefore an acidic medium (pH 4-5). The acid used for adjusting the pH can be an organic acid, preferably acetic acid, which results in a residue-free drying.

For the formation of the desired impervious, homogeneous layer, water for hydrolysis is added, where the molar ratio of water to precursor is 1: 1 to 1: 9, preferably 1: 1. .5 to 1: 2.5.
In order to prepare a paste according to the invention, the layer-forming components can each be used in proportions such that the solids content of the paste is 9-10% by weight.

Suitable formation of the composition gives a paste with a storage stability of> 3 months, wherein no detectable change in viscosity, particle size or coating behavior in the paste is detected during this period.
The residue-free drying of the paste after the surface coating results in an amorphous Al ₂ O ₃ layer, where the drying is performed at a temperature of 300-1000 ° C., preferably about 350 ° C. In suitable coatings, drying takes place within <5 minutes. When drying is performed under so-called heat treatment conditions of 1000 ° C. or higher, a hard crystalline layer having a structure corresponding to corundum is formed.

Al ₂ O ₃ (hybrid) layers dried at temperatures <500 ° C. can be etched using most inorganic mineral acids, but preferably with HF or H ₃ PO ₄ , but with acetic acid, It can also be etched with many organic acids such as propionic acid. Thus, simple post-structuring of the resulting layer is possible.
Suitable substrates for coating with pastes according to the present invention are monocrystalline or polycrystalline silicon wafers (cleaned with HF or RCA), sapphire wafers, thin film solar modules, functional materials (eg ITO, FTO, AZO, Glass coated with IZO or the like), uncoated glass, steel elements and alloys, especially in the automotive sector, and other surfaces used in microelectronics.

  Based on the chosen substrate, the layers formed through the use of pastes according to the present invention are diffusion barriers, printable dielectrics, electrical and electronic passivates, anti-reflective coatings, mechanical protection layers against wear, oxidation Or it can act as a chemical protective layer against the action of acids.

The pastes according to the invention described herein can be coated in a simple manner on a semiconductor material, preferably on silicon and particularly preferably on a silicon wafer, where these correspond to the corresponding treatments. Later, it induces electronic surface passivation. This increases the charge carrier lifetime already, ie after application of a thin layer of paste and subsequent drying. If not only drying but also so-called heat treatment is carried out at a temperature in the range of 350-550 ° C. in any of the forming gas flows (eg 5% v / v H ₂ /95% v / v N ₂ ), the lower layer The surface passivation of can be greatly increased.

  A paste according to the present invention in the form of a hybrid material comprising simple polymeric boron and phosphorous oxides and alkoxides thereof, in particular in the general electrical and electronics industry, and in the photovoltaic industry, in particular crystalline silicon solar cells and It can be used for cheap overall and local doping of semiconductors, preferably silicon, in the manufacture of solar modules.

  Pastes according to the present invention are printable, and the formulation and its rheological properties can meet a wide range of needs for each printing method used. These pastes are preferably printed using flexographic printing and / or screen printing, particularly preferably using screen printing.

The paste according to the invention in the formation of a hybrid sol comprising Al ₂ O ₃ / B ₂ O ₃ can be used for specific doping of semiconductors, preferably silicon wafers. Silicon wafers utilized for this purpose are preferably cleaned with RCA or an alternative equivalent cleaning sequence. Suitable wafer surfaces can be hydrophilic or hydrophobic terminated shapes. Prior to the application of the Al ₂ O ₃ layer, a simplified cleaning is preferably performed; the wafer to be processed is preferably cleaned and etched with an HF solution. The layer remaining on the wafer after the doping process can be easily removed by etching in diluted HF.

The Al ₂ O ₃ layer thus produced can be used as a sodium and potassium diffusion barrier in LCD technology. Here, the thin layer of Al ₂ O ₃ on the cover glass of the display can prevent the diffusion of ions from the cover glass into the liquid crystal phase, allowing the lifetime of the LCD to be significantly increased.

This specification enables those skilled in the art to make comprehensive use of the present invention. Accordingly, it is assumed that the above description will be available to those skilled in the art to the greatest extent without further comments.
If anything is unclear, it goes without saying that the cited literature and patent literature should be considered. Accordingly, these documents are considered part of the disclosure content of this specification.

  For better understanding and to illustrate the present invention, the following are two examples that are within the protection scope of the present invention. These examples also serve to illustrate possible variations. However, due to the general validity of the principles of the invention described, it is not appropriate to reduce the protection scope of the present application to these alone.

Furthermore, it will be appreciated by those skilled in the art that in the examples shown, and in the remainder of the specification, the amount of ingredients present in the composition is always 100% by weight or 100 mole% in total, based on the total composition. From the percentage range shown, even if higher values occur, this cannot be exceeded. Unless otherwise indicated,% data is understood as weight% or mole%, with the exception of ratios, which are given by volume data.
The temperature given in the examples and in the description and in the claims is always ° C.

Example
Example 1:
4.6 g salicylic acid and 1.7 g acetylacetone and 2 g acetic acid in 22 ml diethylene glycol monoethyl ether are initially introduced into a 100 ml round bottom flask. 14.1 g of aluminum tri-sec-butoxide is added to this solution and the mixture is stirred for 10 minutes. For the hydrolysis of the partially protected aluminum alkoxide, 2.8 g of water is added and the yellow solution is stirred for 10 minutes and left for 1 day for aging. The liquid ink is evaporated in a rotary evaporator at a temperature of 50 ° C. and a pressure of 20 mPa and maintained under these conditions for a further 2 hours after distillation of all 2-butanol formed from hydrolysis. The resulting viscous mass exhibits a viscosity of 4.3 Pas. The resolution of the layout applied by screen printing shows a slight “bleed” of the paste, and the printed 100 μm line is about 150 μm wide after drying.

Example 2:
4.6 g salicylic acid and 2.5 g acetylacetone and 1 g acetic acid in diethylene glycol monoethyl ether are initially introduced into a 100 ml round bottom flask. 21.4 g of aluminum tri-sec-butoxide is added to this solution and the mixture is stirred for 10 minutes. For the hydrolysis of the partially protected aluminum alkoxide, 3.7 g of water are added, the yellow solution is stirred for 10 minutes and left for 1 day for aging. The viscous ink is evaporated in a rotary evaporator at a temperature of 50 ° C. and a pressure of 20 mPa and maintained under these conditions for a further 2 hours after distillation of all 2-butanol formed from hydrolysis. The resulting viscous mass exhibits a viscosity of 14 Pas.

Example 3:
After washing with HF, the polycrystalline silicon wafer is printed with the aluminum oxide paste from Example 2 by screen printing. In order to simulate long-term print filling, about 1000 preprints are performed with the paste prior to actual printing. Even after this long-term test, the paste shows very good resolution.
FIG. 2 shows a photomicrograph of the Al ₂ O ₃ layout applied by screen printing after about 1000 preprints. Very good resolution after long-term printing is demonstrated from both photographs (50 μm print on the left side, about 53 μm after drying; 100 μm print on the right side, about 105 μm after drying).

Example 4:
In order to be able to assess the stability of the paste, the viscosity is investigated over a period of at least 6 weeks. FIG. 3 shows the change in viscosity of the paste according to Examples 1 and 2.
From the viscosity curve it is understood that some of the paste thickens, especially within the first few days after synthesis, but the viscosity changes slightly during the remaining shelf life (<2% after 3 days). The viscosity can be reset at any time by adding a small amount of solvent.

Example 5:
After washing, a p-doped (100) FZ silicon wafer piece, polished on both sides, was double-side printed by screen printing with an aluminum oxide sol paste according to Examples 1 and 2, and each printed side was 450 ° C., respectively. Dry on a hot plate for 30 minutes. The print layout is a square with a side of 4 cm. The charge-carrier lifetime of the wafer is subsequently investigated with a WCT-120 photoconductive lifetime tester (QSSPC, quasi-steady state photoconductivity; measurement window 3 cm). The criteria used were identical wafer samples that were either uncoated or processed utilizing the wet chemical quinhydrone / methanol method. The quinhydrone / methanol method (a mixture of 1,4-benzoquinone, 1,4-benzohydroquinone and methanol) is a wet chemistry and temporarily effective, ie electronic surface passivation that is not long-term stable. All wafer samples are pre-etched with diluted HF (previously cleaned).

FIG. 4 graphically illustrates the charge-carrier lifetime of p-doped FZ wafer samples: uncoated sample (yellow, bottom), aluminum oxide coated sample (blue, medium) and chemically passivated. Sample (magenta, top). The lifetimes are in this order (injection density: 1E + 15 cm ⁻³ , identical to carrier density): 8 μs, 275 μs and >> 3000 μs.

An increase in lifetime of about 34 times is judged relative to the uncoated sample. The increase in carrier lifetime is due to the action of aluminum oxide as an electronic surface passivation of the semiconductor material.
It should be noted in this connection that the sample dries only under ambient conditions. An increase in carrier lifetime is expected after sample processing either under oxygen, oxygen / nitrogen, nitrogen or forming gas atmosphere (eg 5% v / v nH ₂ /95% v / v N2). The In addition, edge effects and influences cannot be eliminated in the passivating action, and the effects of defects hidden in the front and back coatings cannot be eliminated.

Claims (15)

Use of a printable, sterically stabilized paste for the formation of Al ₂ O ₃ coatings and mixed Al ₂ O ₃ hybrid layers. From the group of precursors for the formation of Al ₂ O ₃ and boron, gallium, silicon, germanium, zinc, tin, phosphorus, titanium, zirconium, yttrium, nickel, cobalt, iron, cerium, niobium, arsenic, and lead Use of a paste according to claim 1, comprising one or more oxides of selected elements, wherein the paste is obtained by introduction of a corresponding precursor into the paste.   Use of a paste according to claim 1 or 2, sterically stabilized by mixing with at least one hydrophobic component and at least one hydrophilic component, and optionally with at least one chelating agent.   At least one hydrophobic component selected from the group of 1,3-cyclohexadione, salicylic acid and structurally related compounds, and acetylacetone, dihydroxybenzoic acid and trihydroxybenzoic acid or structurally related compounds thereof, Chelating agents such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DETPA), nitrilotriacetic acid (NTA), ethylenediaminetetramethylenephosphonic acid (EDTPA) and diethylenetriaminepentamethylenephosphonic acid (DETPPA), or structurally related complexes Use of a paste according to claim 3, comprising at least one hydrophilic compound selected from the group of agents or corresponding chelating agents.   A solvent selected from low boiling alcohols, preferably selected from the group of ethanol and isopropanol, and preferably selected from the group of diethylene glycol monoethyl ether, ethylene glycol monobutyl ether and diethylene glycol monobutyl ether or mixtures thereof; At least one high boiling solvent selected from the group of high boiling glycol ethers, and optionally a polar solvent selected from the group of acetone, DMSO, sulfolane and ethyl acetate or a similar polar solvent. Use of the paste according to 3 or 4.   6. Use of a paste according to claim 3, 4 or 5, comprising one or more organic acids, preferably acetic acid, having an acidic pH in the range of 4-5 and resulting in a residue-free drying as acid.   Water for hydrolysis is added in a water to precursor molar ratio in the range of 1: 1 to 1: 9, preferably between 1: 1.5 and 1: 1.25, where solids 7. Use of a paste according to any one of claims 1 to 6 for the formation of an impermeable homogeneous layer, the minutes being in the range of 9 to 10% by weight.   8. Any of claims 1 to 7 for the manufacture of diffusion barriers, printed dielectrics, electrical and electronic passivators, anti-reflective coatings, mechanical protective layers against wear or chemical protective layers against the action of oxidation or acid. Use of the paste according to one item.   8. Paste according to any one of claims 1 to 7, for the preparation of a hybrid material comprising a simple polymeric boron and phosphorous oxide and its alkoxide for the overall or local doping of a semiconductor, preferably silicon. Use of. For the production of the Al ₂ O ₃ layer as the sodium and potassium diffusion barriers in LCD technology, the use of paste according to any one of claims 1 to 7. On monocrystalline or polycrystalline silicon wafers, sapphire wafers, thin film solar modules, glass coated with functional materials (eg ITO, FTO, AZO, IZO or similar), uncoated glass, steel elements and alloys And a method for producing a pure, residue-free, amorphous Al ₂ O ₃ layer on other materials used in microelectronics, according to claim 1. Said method, characterized in that after application of the paste, drying is carried out at a temperature between 300 and 1000 ° C., preferably at 300 to 400 ° C., particularly preferably at 350 ° C.   The method according to claim 11, wherein a hard, crystalline layer having properties equivalent to corundum is formed by drying and heat treatment at a temperature from 1000 ° C.   12. The method of claim 11, wherein drying is performed for less than 5 minutes, resulting in a layer having a thickness of less than 100 nm. Pure, residue-free, amorphous, A method according to claim 11 for producing a structured possible the Al ₂ O ₃ layer, as claimed in any one of claims 1 to 7 Paste Wherein the thin layer is applied and then dried at a temperature between 300 ° C. <X <500 ° C. Drying the applied paste layer at a temperature of <500 ° C. gives a layer that can be post-structured in a simple manner with HF, H ₃ PO ₄ or organic acids such as for example acetic acid or propionic acid The method according to claim 14, characterized in that: